Elwood Blues is released from prison after serving eighteen years for the events of the previous film and is informed that his brother, "Joliet" Jake Blues, has died. He is picked up by Matara, a dancer who works for the Blues Brothers' former drummer Willie Hall, who now runs a night club. Willie gives Elwood a job to help him get back on his feet.
Before meeting up with Willie, Elwood asks to be dropped off to see Sister Mary Stigmata, who is now working at a hospital after the St Helen of the Blessed Shroud Orphanage was closed, despite Jake and Elwood's efforts to save it. She informs him that Curtis, his surrogate father, has also died, but that he had years ago fathered an illegitimate son, Cabel Chamberlain, who is now an Illinois State Police commander. She also introduces Elwood to a ten year old orphan, Buster, and encourages him to become the boy's mentor.
Against Stigmata's advice, Elwood tracks down Cabel at his police headquarters, to inform him of his real father, and to ask him to join The Blues Brothers Band, which he plans on reforming. Cabel, upset by the news and offended by the suggestion to join him after learning of Elwood's and Jake's criminal history, throws him out of the building where Buster steals his wallet, containing enough money for Elwood to purchase a new Bluesmobile at a police surplus lot - in the same vein as its predecessor, a 1990 Ford "Crown Vic" police car.
Elwood and Buster begin tracking down members of the former band to recruit them from their current jobs. Willie runs a strip club and joins after it is burned down by the Russian mafia, but not before Elwood enlists the help of Willie's barman, "Mighty" Mack McTeer, to try to convince them to leave the club alone; Mack becomes the new lead singer of the band. Two other members, Matt "Guitar" Murphy and "Blue" Lou Marini, join again against the advice of Murphy's wife, with whom they now run a Mercedes-Benz car dealership. Three members (Steve "The Colonel" Cropper, Donald "Duck" Dunn and Tom "Bones" Malone) work at a radio station and quickly agree to join, Alan "Mr Fabulous" Rubin (who now works as a funeral director) is forced to join against his will after Elwood insults the Russian mafia (for whom Mr Fabulous has organised a funeral) again, and finally Murphy Dunne joins after his boss at a call center gives him permission.
The newly reformed band uses their old agent, Maury Sline, to book them a show. On the way to the show, they are followed by Cabel and the Illinois and Indiana state polices, who are now looking for Elwood for stealing Cabel's wallet earlier, and believing that he has kidnapped Buster. Later even the FBI joins the chase. While avoiding a police roadblock Elwood interrupts a white supremacist militia group meeting, unintentionally destroying their boat full of explosives they planned to use. The band arrives at the show to find they have been mistakenly booked as a Bluegrass Band, but they perform the show anyway. Afterwards, they evade capture by the police. However, en route to the next concert, the Bluesmobile runs out of fuel and the band threatens to quit, with Elwood acknowledging defeat. But Buster inspires Elwood to give an impassioned speech defending blues music, and the band relents, accompanying him again - save Blue Lou, who, in a rare show of intelligence, goes to get fuel for the Bluesmobile.
The police catch up with the band at a tent revival where Elwood's old friend Reverend Cleophus James is preaching. Before Cabel can arrest them he has an epiphany brought on by Reverend Cleophus that he should join the band instead of being a police officer - and magically trades in his police uniform for a Blues Brothers black suit, black hat and sunglasses. The band evades capture once more, now with Cabel joining them, although his fellow police officers believe the band members have brainwashed him.
The band continues on to their next booking, a tryout for a Battle of the Bands put on by Queen Mousette, allegedly a 130-year-old cannibalistic voodoo witch. Queen Mousette requests the band play something Caribbean, and when Elwood explains they don't play that kind of music, she casts a spell on them to play anyway. Mousette accepts the band into the battle; however, at the song's conclusion, Elwood, Mack, and Cabel are turned into hollow plastic statues, forcing the band to stay overnight.
At the show, Queen Mousette undoes the spell to allow the Blues Brothers band to play against the Louisiana Gator Boys; a supergroup of blues musicians, one of whom is Malvern Gasperone, who sold Elwood the Bluesmobile. The Louisiana Gator Boys win the battle. After the battle, the show is interrupted by the arrival of both the Russian mafia and the militia group from earlier, both of whom are turned into rats by Queen Mousette when they threaten a shootout. The Illinois state police arrive, but stand down after Cabel informs them that he is all right and with the band by choice. Elwood suggests that two bands jam together on stage, which they do, and when Stigmata arrives, he uses the performance as cover to say goodbye to Cabel and Mack and escape with Buster, with the police giving chase.
The Blues Brothers Band
Dan Aykroyd as Elwood J. Blues – harmonica and vocals
John Goodman as "Mighty" Mack McTeer – lead vocals
Joe Morton as Commander Cabel Chamberlain/Cab Blues – vocals
J. Evan Bonifant as Buster Blues – vocals and harmonica (harmonica recorded by John Popper)
Steve Cropper as Steve "the Colonel" Cropper – rhythm guitar and vocals
Donald "Duck" Dunn as Donald "Duck" Dunn – bass guitar
Murphy Dunne as Murphy "Murph" Dunne – keyboards
Willie Hall as Willie "Too Big" Hall – drums and percussion
Tom Malone as Tom "Bones" Malone – trombone, tenor saxophone and vocals
Lou Marini as "Blue Lou" Marini – alto saxophone and tenor saxophone and vocals
Matt Murphy as Matt "Guitar" Murphy – lead guitar
Alan Rubin as Alan "Mr. Fabulous" Rubin – trumpet, percussion and vocals
Musical guests
Erykah Badu as Queen Moussette
Blues Traveler as themselves
Lonnie Brooks as himself
Eddie Floyd as Ed
Aretha Franklin as Mrs. Murphy
James Brown as Reverend Cleophus James
Jonny Lang as janitor
Sam Moore as Reverend Morris
Wilson Pickett as Mr. Pickett
Junior Wells as himself
The Louisiana Gator Boys
The Louisiana Gator Boys is a blues supergroup created for the film. They face The Blues Brothers in a Battle of the Bands. The band is composed of:
Jeff "Skunk" Baxter – guitar
Gary U.S. Bonds – vocals
Eric Clapton – vocals and guitar
Clarence Clemons – vocals, tenor saxophone and tambourine
Jack DeJohnette – drums
Bo Diddley – vocals and guitar
Jon Faddis – trumpet
Isaac Hayes – vocals
Dr. John – vocals and piano
B.B. King as Malvern Gasperone – vocals and guitar
Tommy "Pipes" McDonnell – vocals
Charlie Musselwhite – vocals and harmonica
Billy Preston – vocals and synthesizer
Lou Rawls – vocals
Joshua Redman – tenor saxophone
Paul Shaffer as Marco/Himself – keyboards
Koko Taylor – vocals
Travis Tritt – vocals and guitar
Jimmie Vaughan – vocals and guitar
Willie Weeks – bass guitar
Steve Winwood – vocals and organ
Kathleen Freeman, Frank Oz, Steve Lawrence, and Jeff Morris appeared in cameos, all reprising their roles from The Blues Brothers film. Nia Peeples portrays a state police lieutenant who serves as Cabel's second-in-command, Darrell Hammond as Robertson the militia leader, John Lyons as a Russian thug, and Paul Shaffer as Marco, Queen Moussette's majordomo. The film is dedicated to John Belushi, Cab Calloway, and John Candy, cast members from the original film who had died prior to the sequel's production.